The following relates to the positional encoder arts, nuclear reactor arts, nuclear reactor operating arts, and related arts.
Pressure vessels advantageously enable the creation of high pressure environments, which are optionally also at high temperature. For example, nuclear reactors of the pressurized water reactor (PWR) variety employ a pressure vessel to maintain primary coolant water in a sub-cooled state that suppresses void (i.e. bubble) formation and increases efficiency of the primary coolant in performing neutron moderator and thermal transport operations. In one contemplated PWR design, the subcooled primary coolant water is expected to be maintained at a pressure above 16.0 MPa and a temperature above 550° F., with some differences between the hot and cold legs of the primary coolant flow circuit. This is merely an illustrative example, and the design operating temperatures and pressures depend upon the specific reactor design. Other useful applications of pressure vessels include steam drums, various material processing systems that subject material to high temperature and/or pressure, chemical processing systems, and so forth.
Producing motion inside a pressure vessel is a challenging task, due to the high pressure, optional high temperature, and other factors. One approach is external magnetic coupling through the pressure vessel wall, but this approach has practical access limitations. Another approach is to use a bellows, but this also has access limitations, and moreover the long-term mechanical stress on the bellows can lead to component failure. Another approach is to employ a glandless or glanded mechanical vessel penetration, but this has similar problems.
A more flexible approach to providing motion inside a pressure vessel is to employ a canned internal motor that is disposed inside the pressure vessel. For example, the mPower™ reactor design is contemplated to include canned motors disposed inside the reactor pressure vessel for operating the control rod drive mechanisms (CRDMs), and other reactor designs contemplate employing internal reactor coolant pumps (RCPs) with canned motors. These approaches tend to require higher levels of engineering expertise and design since the materials of the motor must be capable of withstanding the high temperature and pressure inside the pressure vessel, and any components immersed in the primary coolant water should also be robust against long-term exposure.
A related problem is to perform measurement of mechanical motion at high temperature and/or pressure. This problem arises in both testing and operational phases of the deployment of a pressure vessel-based system. For example, validation of the mPower™ reactor design is expected to include testing of CRDM units at operational temperature and pressure in a test facility prior to deployment in an operational reactor. While operation of the CRDM may be inferred from measuring electrical input and response of the operating CRDM motor, and from post-testing inspection of the CRDM unit, it would be desirable for the testing to include direct measurement of the motion generated by the CRDM in the pressure vessel at operational temperature and pressure.
Performing motion measurement in a high pressure and/or high temperature environment faces similar problems to those faced in producing motion in such environments. Additionally, cost is a more significant issue, especially for sensors used in testing. It is not desirable for test sensors to be expensive components, since they are not operational elements of the nuclear reactor. However, the test sensors should be robust and reliable in order to produce valid test data.